Transformers (movieverse), Sam/Optimus Prime, body ar
Kinda ended up Optimus Prime/Sam + the Autobots, but, hey, who's counting?
o o o
Sam shivered as huge fingers ghosted over his bare skin, leaving behind a thin film of almost liquid. Incredibly small metal shavings, suspended in a viscous oil of an indeterminable origin, painted over his skin like the ceremonial paint of ancient warriors. Gold, silver, black iron, red-green copper, faintly blue tungsten, other alloys he didn't recognize off the top of his head, swirling over his limbs and back in not-quite organic swoops and curls. Impossibly thin wires were already braided into his hair and around his body, marking guides for the paints in nickel and cobalt and tin.
Gentle hands urged him to turn around and he did carefully, willingly, twisting and staring up, up, at the sparkle-spangle of the night sky and glowing blue eyes. A metal mouth smiled, a metal hand rose, and the designs continued; the sharp lines of the Matrix over his heart, twisted spirals of manganese and iron around the scars on his neck and belly, slow tungsten loops on his cock. He shuddered at that last, his hips bucking once. A mildly reproving click came from above and he trembled to hold still, while those incredible metal fingers closed over his erection in a way that should have been physically impossible. He was stroked, milked, brought to a quaking orgasm with a moan caught behind clentched teeth, and the moisture of his seed was wicked away without disturbing his new paint job even once.
"You have fought for us," Optimus Prime rumbled, finishing the last few strokes of copper on Sam's face. "You have proved yourself, in more ways than any of us can count, that you are worthy of our respect, our gratitude, and our friendship. We welcome you, Sam Witwicky, as one of our own. We mark you now, in the way of our kind, and though we cannot seat these patterns on your skin as we can our own, all of us here will remember, so that all who come later may know what you have done."
Sam looked around, at the ring of blue optics that witnessed this. All of them, stripped of their disguises and kibble, and even in the dim lighting, he could pick out the designs they all wore; copper and steel and platinum and gold and every element he currently wore, plus a few too toxic for him. The same fluid swirls, the same shapes that described a thousand life times of war and peace and duty and love and hate and great deeds and great sorrows. He bowed his head, mostly because he couldn't think of anything to say that didn't sound shallow or contrived.
"But," Optimus continued, scooping Sam up into his hands, earning a startled squawk. "Since humans cannot handle the absorption of large amounts of metal, I am afraid we must now remove them." Hands descended on him from every direction; rubbing, swiping, cleaning away every fleck of the metallic paint, deliberately arousing, and Sam grinned and let them all do as they pleased.